Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$243.56	6.760%	$260.0247	$260.02	$260.00	$260.00
Purchase #2	$53.33	11.491%	$59.4582	$59.46	$59.45	$59.50
Purchase #3	$223.55	12.302%	$251.0511	$251.05	$251.05	$251.10
Purchase #4	$178.42	8.769%	$194.0656	$194.07	$194.05	$194.10
Purchase #5	$207.69	4.551%	$217.142	$217.14	$217.15	$217.10
Purchase #6	$187.85	6.181%	$199.461	$199.46	$199.45	$199.50
Purchase #7	$59.71	3.153%	$61.5927	$61.59	$61.60	$61.60
7 purchase totals =	$1,154.11		$1,242.7953	$1,242.79	$1,242.75	$1,242.90